JPH0580755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an error detection and correction method in a magnetic recording/reproducing device.

When a magnetic recording/reproducing device, such as a magnetic tape device, writes or reads data while the magnetic head is substantially in contact with the magnetic recording medium, dust generated from the magnetic recording medium or external dust may come between the magnetic recording medium and the magnetic head. In many cases, consecutive errors commonly called burst errors occur. In such cases, it is necessary to detect and possibly correct the burst errors that have occurred.

[Prior art]

Magnetic recording and reproducing devices, especially magnetic recording and reproducing devices such as cassette tape devices that are realized at low cost by having fewer write/read channels, require 1
Recording and playback is often done in track serial or two-track parallel. In such devices, when recording data on magnetic tape,
In a segment that constitutes a unit of writing or reading, an error detection code for detecting errors is added to the information data in the segment to form segment data, and multiple segment data are sequentially exclusive-ORed. By adding a segment containing the created data as an error correction code to one group of a plurality of segments related to the plurality of segment data, errors in the information data are detected and corrected.

FIG. 2 is a diagram for explaining a state in which a data group consisting of an A segment group and a B segment group is serially recorded on one track based on the conventional method as described above. In the figure, SEG stands for Segment.
, ECC is an error correction code (Error
correcting code). The A segment group is composed of N segments SEG0A, SEG1A...SEGNA containing information data and an ECC segment containing an error correction code ECC.A, and these segments are serially recorded. On the other hand, the B segment group
Similar to the A segment group, N segments SEG0B, SEG1B... containing information data.
ECC including SEGNB and error correction code ECC・B
These segments are serially recorded following the A segment group. As shown in FIG. 2, a segment containing information data is composed of a resynchronization signal, information data, and an error correction code for correcting errors in this information data. - Forming data.

Meanwhile, the error correction code for each ECC segment
Data E A and E B of ECC・_A and ECC・_B are defined by the following equations.

A ₀ A ₁ ...A _i ...A _N =E _A (1) B ₀ B ₁ ...B _i ...B _N =E _B (2) Here, generally A _i and B _i are the A segment group and the B segment group. each represents the segment data of the i-th segment of the group,
is exclusive OR (sometimes abbreviated as EOR)
represents. That is, the error correction code data E _A and E _B are created by sequentially exclusive ORing the segment data of each segment group.

From equations (1) and (2) above, A _i =A ₀ A ₁ …A _i-1 A _i+1 …A _N E _A (3) B _i =B ₀ B ₁ …B _i-1 B _{i+ 1} …B _N E _B (4) is derived. These formulas indicate that segment data is equal to the sequential exclusive OR of the remaining segment data of the segment group to which it belongs and the error correction code data of that segment group. Therefore, it can be seen that if there is an error in the segment data of one segment for one segment group, correct segment data can be found and corrected using the above formula.

Error detection in conventional magnetic recording and reproducing devices is based on the above idea, and errors in information data are detected using the error detection code of each segment, and the erroneous segment data is corrected using the error correction code of each segment group. are doing.

[Problem that the invention seeks to solve]

In conventional error detection and correction methods, (3) and
As is clear from equation (4), it is possible to correct one segment data error in one segment group, but if segment data errors occur in multiple segments, for example, two adjacent segments. The drawback is that sometimes it is no longer possible to correct it.

Furthermore, errors may occur across a plurality of adjacent tracks, and it is necessary to take measures to prevent this.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to provide an error detection and correction method for a magnetic recording/reproducing apparatus that solves the above-mentioned problems.

The present invention provides that one segment group includes a plurality of segments including segment data each consisting of information data and an error detection code added to the information data to detect an error in the information data; A segment containing error correction code data created by sequentially exclusive ORing each segment data, and a plurality of segment groups are arranged on a track of a magnetic recording medium, and the information data is read out. In an error detection and correction method for a magnetic recording/reproducing device, which has an error correction mechanism that corrects an error in the segment from an error correction code and an error correction code, a plurality of segment groups of the segment groups are grouped together, and each segment group is The segments constituting the segment are distributed and arranged on the same number of tracks as the plurality of tracks, and in each of the plurality of segment groups, Each segment is arranged on the plurality of mating tracks so as to be adjacent to segments of different segment groups.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a diagram showing a configuration example considered as a premise of the present invention, and explains the recording state when a data group consisting of an A segment group and a B segment group is serially recorded on one track. This is a diagram for Note that the configurations of the A segment group and B segment group in this configuration example are the same as those explained in FIG. 2, but the error detection code added to the information data of each segment is, for example, CRC.
(Cyclic Redundancy Check) code can be used.

As is clear from FIG. 3, in one-track serial recording, the segments of the A segment group and the segments of the B segment group are
SEG0A, SEG0B, GEG1A, SEG1B…SEGNA,
Arrange them alternately like SEGNB, ECC・A, and ECC・B. According to this arrangement, if a burst error occurs in two segments, one of the two segments will be assigned to the A segment.
It is clear that one belongs to the B segment group and the other belongs to the B segment group. Therefore, since each segment group has a one-segment data error, error correction can be performed for each segment group.

The configuration shown in FIG. 3 is sufficiently effective as a countermeasure against errors in segment data. However, as shown in FIG. 3, a configuration in which each segment in one segment data of a plurality of segment data is arranged adjacent to other segment data is difficult to use when writing or reading, for example, a magnetic disk. It exists as a technology to reduce rotation waiting time.

With this in mind, the present invention addresses errors across multiple tracks.

FIG. 4 is a diagram for explaining an embodiment in which a data group consisting of an A segment group and a B segment group is recorded on two tracks, track 0 and track 1, in parallel. As is clear from this figure, track 0 has segments of the A segment group and segments of the B segment group, SEG0A, SEG1B,
SEG2A, SEG3B...SEGNB, ECC・A are arranged alternately, and the segments of the A segment group and the segments of the B segment group are placed on track 1, SEG0B, SEG1A,
Arrange alternately like SEG2B, SEG3A...SEGNA, ECC・B. According to this arrangement, even if a burst error occurs across the segments of track 0 or track 1, each segment group will have a single segment data error, so the error will be ignored for each segment. error correction becomes possible.

The above embodiment is for two-track parallel recording, but even when parallel recording is performed on three or more tracks, the segments of the A segment group and the segments of the B segment group are arranged alternately on each track. You should do it. Furthermore, the data group is not limited to a data group consisting of two segment groups, but even if the data group is a data group consisting of a plurality of, for example, n sets of segment groups, the segments of each segment group may overlap the segments of other segment groups. It is obvious that they should be placed alternately on the track so that they are adjacent to each other. In this case, even if a burst error occurs over n segments on the track, it is possible to correct the error.

Next, a circuit for detecting and correcting errors in a magnetic recording/reproducing apparatus that records on tracks of a magnetic recording medium as described above will be described.

FIG. 1 shows an error detection and correction circuit for detecting and correcting errors occurring in a data group consisting of an A segment group and a B segment group recorded in parallel on two tracks as shown in FIG. Note that this circuit is A segment/
Only the error detection and correction circuit for the group is shown, and although there is an identical error detection and correction circuit for the B segment group, it is omitted from the drawing. In the figure, 1 is a first data buffer in which segment data and error correction codes of segments belonging to the A segment group among data read from a magnetic recording medium are serially transferred and stored; 2 is a first data buffer; This is an error detection circuit that detects errors in information data based on error detection codes added to the information data of each segment. The error detection circuit 2 normally generates a logic "1" signal, and is configured to generate a logic "0" signal when an error in information data is detected. 3
is supplied with the output signal of the error detection circuit 2, and A
This is an error counter that counts the number of segment data errors in a segment group, and is a multi-segment data error that is one segment data error or two or more segment data errors.・Output information indicating whether there is an error. 4 is a segment counter that counts the number of segments when the segments of the A segment group are sequentially supplied to the first data buffer 1; A register 5 stores the count value of the segment counter 4 when the first "0" signal is input from the error detection circuit 2. Reference numeral 6 denotes an AND circuit that performs an AND operation between one segment of data output in parallel from the first data buffer 1 and the output signal of the error detection circuit 2. Reference numeral 7 denotes an error pattern register, which is a register in which correct segment data is finally stored in the case of a one-segment data error, as will be described later. And this error pattern register 7
Initially, all "0" are set. 8 is
AND circuit 6 output data and error pattern
This is an EOR circuit that performs EOR on the data stored in register 7 on a bit-by-bit basis.The output data of the EOR circuit is sent to error pattern register 7, and the data stored in error pattern register 7 is will be replaced with the data of 9 is
This is a second data buffer to which the output data from the AND circuit 6 and the data stored in the error pattern register 7 in the case of a one-segment data error are supplied. 10 is a NOT circuit which negates the output data from the error pattern register 7; 11 is a NOT circuit to which the output signal of the error detection circuit 2 is supplied to the set input terminal S, and which outputs the multi-segment data of the error counter 3;
This is a flip-flop whose reset input terminal R is supplied with a "1" signal indicating the occurrence of an error. 12
is supplied with the output data from the NOT circuit 10, the output signal of the flip-flop 11, and a data end signal indicating that reading of the data of the A segment group has been completed, that is, a "1" signal, and information indicating the presence or absence of an error. NAND that outputs
It is a circuit.

Next, the operation of the error detection and correction circuit shown in Fig. 1 is as follows.
The case where there is no segment data error, the case where there is one segment data error, and the case where there are two or more segment data errors will be explained separately.

When there is no segment data error; As shown in Figure 4, read the data group consisting of the A segment group and B segment group recorded on the magnetic recording medium, and sequentially read the data of the A segment group segment by segment. , i.e. segments SEG0A, SEG1A…SEGNA,
The data is serially transferred and stored in the first data buffer in the order of ECC and A. The segment counter 4 counts the number of segments sent to the first data buffer. Error detection circuit 2
detects an error in the information data of segment SEG0A, which is first stored in the first data buffer, using an error detection code added to this information data. There are no errors in the information data now, so
The error detection circuit 2 outputs a "1" signal, and this "1" signal is input to one input terminal of the AND circuit 6 and the set input terminal of the flip-flop 11, respectively. Flip-flop 11 is set and outputs a "1" signal. On the other hand, the segment data stored in the first data buffer 1 is input in parallel to the other input terminal (multiple input terminals) of the AND circuit 6.
The data is transferred to the second data buffer 9 and stored therein, and is also input to the EOR circuit 8.

In the EOR circuit 8, the segment data inputted from the first data buffer 1 and all "0" stored in the error pattern register 7 are processed.
The data is EORed bit by bit, and the result is input to the error pattern register 7, replacing all "0" data.

In the manner described above, the segment data is sequentially processed and all segment data of the A segment group is stored in the second data buffer 9. Error correction code segment ECC A, which is the last segment of the A segment group
When the error correction code is input to the first data buffer 1, the error correction code is input to the EOR circuit 8 via the AND circuit 6. In this case, the error correction code is generally not stored in the second data buffer. The EOR circuit 8 performs the final EOR calculation, and the final result is stored in the error pattern register 7. As is clear from equations (1) and (3) above, if there is no error in all segment data, A ₀ A ₁ . . . A _N E _A will be all "0". Therefore, the final content of the error pattern register 7 is all "0", and this all "0" data is input in parallel to the NOT circuit 10, inverted to all "1" data, and sent to the NAND circuit. The signals are input in parallel to 12 input terminals. On the other hand, the flip-flop 11 is in the set state and outputs a "1" signal, and this "1" signal is input to the NAND circuit 12. Therefore, when a "1" signal indicating the data end is input to the NAND circuit 12,
A "0" signal is output, and this "0" signal indicates that there is no error in the segment data of the A segment group. The error-free segment data stored in the second data buffer is then output.

In the case of one segment data error: When segment data with an error is transferred to the first data buffer 1, the error detection circuit 2 outputs a "0" signal. This "0" signal is input to one input terminal of the register 5, error counter 3, and AND circuit 6. register 5
reads the count value of segment counter 4 at that time. This count value indicates the number of the segment in which the error occurred. On the other hand, the count value of error counter 3 becomes 1, indicating that there is a 1 segment data error.

As a result of the AND circuit 6 being inhibited by the "0" signal of the error detection circuit 2, the segment data with the error in the first data buffer is not stored in the second data buffer 9, and is stored in the second data buffer 9. That area of 9 becomes all "0".

When the input of all segments of the A segment group is completed, the data finally stored in the error pattern register 7 matches the segment data in which the error occurred, as is clear from the above formula (3). ing. Therefore, if the data in the error pattern register 7 is input to the second data buffer and stored in the all "0" data area indicated by the register 5, the error-corrected A segment will be created. - All segment data of the group can be output from the second data buffer.

On the other hand, due to one segment data error,
The bit pattern that is the contents of the error pattern register 7 always contains at least one "1" bit, and therefore the output of the NOT circuit 10 always contains a "0" bit. .
Therefore, when a data end signal "1" is input to the NAND circuit 12, the NAND circuit 12 outputs a "1" signal, and this "1" signal indicates that there is an error in the segment data of the A segment group. It shows that

In the case of 2 or more segment data errors; If there are 2 or more segment data errors in the A segment group, the count value of error counter 3 will be 2 or more, indicating that there is a multi-segment data error. It is shown that. In the case of a multi-segment data error, the segment data in the second data buffer cannot be corrected. In such a case, the bit pattern of the final data in the error pattern register 7 almost always includes "1", and when the data end signal "1" is input to the NAND circuit 12, the NAND circuit 1
2 outputs a "1" signal, indicating that a data error has occurred.

However, in some cases, the final data in the error pattern register 7 may be all "0". In such a case, if flip-flop 11 remains set, the NAND
Circuit 12 will output a "0" signal, giving erroneous information that there is no error despite the multi-segment data error.

To prevent such a situation, in the case of a multi-segment data error, a reset signal indicating the occurrence of a multi-segment data error of the error counter 3 is input to the reset input terminal R of the flip-flop 11. The flip-flop 11 is reset so that the flip-flop outputs a "0" signal. Therefore, even if the contents of the error pattern register 7 are all "0", the output of the NAND circuit 12 will be "1", making it possible to indicate the occurrence of an error.

The error detection and correction for the A segment group data has been explained above, but it is also possible to perform error detection and correction for the B segment group using another circuit similar to the error detection and correction circuit shown in FIG. it is obvious.

Next, with reference to FIG. 5, an example will be described in which data recorded in the format shown in the figure is separated into segments of the A segment group and segments of the B segment group.

In the figure, 13 reads a data group serially recorded on a magnetic recording medium with a magnetic head;
A shift register in which the demodulated results are stored as serial data. A decoder 14 reads out the data serially stored in the shift register 13 in parallel and detects a synchronization pattern recorded at the boundary with the segment. 15 is a data buffer for storing segment data of the A segment group; A data buffer 16 stores segment data of the B segment group. Reference numeral 17 indicates a flip-flop circuit which outputs a write enable signal which is alternately inverted by the synchronization pattern detection signal from the decoder 14 and which enables the data buffers 15 and 16 to alternately take in data.

Data recorded on a magnetic recording medium has a synchronization pattern recorded at the boundary of each segment. This synchronization pattern is a specific pattern that does not exist in the data, and by detecting this pattern, segment boundaries are detected and segments belonging to each group are separated.
Serial data recorded on magnetic recording media is
The signal is demodulated, transferred in predetermined byte units, and stored in the shift register 13. shift register 13
The data stored in the decoder 14 is read out in parallel and input to the decoder 14.

On the other hand, the data read out from the shift register 13 is also sent to the data buffers 15 and 16, and the flip-flop circuit 17 stores the data in the data buffer 15 or 16 to which the write enable signal is output. Data continues to be stored in either one of the data buffers 15 or 16 until the decoder 14 detects a synchronous turn. When the synchronization pattern is detected by the decoder 4, the flip-flop circuit 17 is inverted by this detection output, and the data buffer 15 or 16 on the side different from the data buffer 15 or 16 that was previously in the write enable state is
is set to write enable, and data is stored until the next synchronization pattern is detected.

In this way, a series of segment data is separated into segment groups and stored in the data buffers 15 and 16. Thereafter, the contents of this data buffer 15 or 16 are transferred to the first data buffer 1 explained in FIG. 1, and error detection and correction of the data is performed.

〔effect〕

As explained above, according to the present invention, one segment group is composed of a plurality of segment data each including information data and an error detection code added to the information data to detect an error; When a data group consisting of n segment groups is recorded on a track of a magnetic recording medium, the segments of each segment group are Since the segments of the segment groups are arranged alternately adjacent to each other, even if a burst error occurs across n segments, for each segment group, only one segment
Since it is a data error, it is possible to detect and correct the error. Therefore, according to the present invention, it is possible to provide an error detection and correction system that is particularly suitable for a cassette tape device that records and reproduces data on a one-track serial or two-track parallel basis and has a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an embodiment of the error detection and correction method of the magnetic recording and reproducing apparatus of the present invention, and FIG. 2 is a diagram for explaining the recording state of segments on a track of a magnetic recording medium using the conventional error detection and correction method. FIG. 3 is a diagram showing a configuration example considered as a premise of the present invention, and FIG. 4 is a diagram for explaining the recording state of segments on tracks of a magnetic recording medium in an embodiment of the present invention. , FIG. 5 is a diagram for explaining an example of separating data recorded on a magnetic recording medium into segments and groups. In the figure, 1 is a first data buffer, 2 is an error detection circuit, 3 is an error counter, 4 is a segment counter, 5 is a register, 6 is an AND circuit,
7 is an error pattern register, 8 is an EOR circuit, 9 is a second data buffer, 10 is a NOT circuit, 11 is a flip-flop, and 12 is a NAND circuit.

Claims (1)

[Scope of Claims] 1. A segment group includes a plurality of segments each including segment data consisting of information data and an error detection code added to the information data to detect errors in the information data; A segment containing error correction code data created by sequentially exclusive ORing each segment data of the segment, and a plurality of segment groups are arranged on a track of a magnetic recording medium and read out. In an error detection and correction method for a magnetic recording/reproducing device having an error correction mechanism for correcting errors in the segment from information data and an error correction code, a plurality of segment groups of the segment groups are combined, and the segment group is The segments constituting the group are distributed and arranged on the same number of tracks as the plurality of tracks, and in the plurality of segment groups, each segment group is 1. An error detection and correction system in a magnetic recording/reproducing apparatus, characterized in that each segment of the track is arranged on each of the plurality of tracks so as to be adjacent to a segment of a different segment group.